Stat update slow for large database in the backend

The current implementation of _update_stats_internal is quite slow in updating the stats.
As a proposal, we could let the database handle score updates and stat updates using a SQL Trigger on the text_label table. Additionally, we could also create an SQL function that can be executed by the backend to update the cached stats.
And if we implement a SQL trigger and function, we may need to reconsider how the cached_stats work

If the proposition seems interessting I could try to dev it 😄

Start by locating _update_stats_internal and tracing how the text_label table and cached_stats are updated. Review the proposed SQL trigger and backend-invoked SQL function approach, then measure stat-update behavior on a large database. Done should include a concrete design and evidence that cached statistics remain correct while updates are faster.